1. Field of the Invention
The present invention is directed to a torsional vibration damping arrangement such as can be used, for example, in the drivetrain of a vehicle to damp and as far as possible eliminate rotational irregularities.
2. Description of the Related Art
Especially in drivetrains constructed with internal combustion engines, a constant torque can generally not be introduced into a drivetrain because periodic ignitions occur in the internal combustion engines and the energy released as a result is converted into a rotational movement of the crankshaft. The torque delivered by the crankshaft and the rotational speed thereof are both subject to fluctuations and oscillations or, generally speaking, rotational irregularities. Because rotational irregularities of this type may be noticeable in driving mode, a general objective is to eliminate these rotational irregularities as far as possible.
For example, it is known to use energy accumulators or energy storages, i.e., for example, springs or moving masses or combinations thereof, to temporarily store the energy occurring in rotational irregularities of the kind mentioned above and then to guide it into the drivetrain in such a way that a smoother speed characteristic or torque characteristic can be achieved. Two-mass flywheels are an example of torsional vibration damping arrangements operating in this manner. Mass pendulums known as mass dampers convert the rotational irregularities occurring in driving condition into oscillating deflections of vibrating masses; the deflection is carried out in opposition to centrifugal force and, by predefining the deflection path and the masses to be deflected, it is possible to tune to particular excitation speeds or excitation frequencies. Mass dampers of this type can, of course, be combined with systems of masses which execute oscillations through the use of springs or the like.
Because of the increasingly restricted space availability in modern vehicles, there is also less installation space available for the systems used for vibration damping with consequent loss of decoupling quality, i.e., in the reduction of occurring rotational irregularities.
It is the object of the present invention to provide a torsional vibration damping arrangement of compact construction which achieves an improved reduction of rotational irregularities introduced into a drivetrain.
According to the invention, this object is met through a torsional vibration damping arrangement, particularly for the drivetrain of a vehicle, comprising an input region to be driven in rotation around an axis of rotation and an output region, wherein a first torque transmission path and parallel thereto a second torque transmission path and a coupling arrangement for guiding together and superposing the torques transmitted and occurring via the torque transmission paths are provided between the input region and the output region, wherein a first phase shifter arrangement is provided in the first torque transmission path for generating a phase shift of rotational irregularities transmitted via the first torque transmission path relative to rotational irregularities transmitted via the second torque transmission path.
In the torsional vibration damping arrangement according to the invention, it is ensured through the use of the phase shifter arrangement that a destructive superposition of oscillation components occurs in the torque to be transmitted in that the transmitted torque is first divided and then recombined by the phase shift that is introduced. Ideally, the rotational irregularities are virtually completely eliminated at least in a particularly critical frequency range.
In order that this phase shift can be achieved efficiently in a structurally simple manner, the first phase shifter arrangement comprises a first oscillation system having a primary side and a secondary side which is rotatable relative to the primary side around the axis of rotation against the force of a spring arrangement.
The first phase shifter arrangement is accordingly constructed substantially on the basis of the operating principle of a two-mass oscillator in which two masses, i.e., essentially the primary side and secondary side, oscillating relative to one another against the action of the spring arrangement are provided with a desired oscillation behavior through selection of spring stiffness on the one hand and of mass ratios and inertia at the primary side and secondary side on the other hand. An oscillation system of this kind characteristically has a resonant frequency. In the frequency range below the resonant frequency, an oscillation system of this kind exhibits subcritical oscillations, i.e., excitation and reaction of the system occur substantially simultaneously. When the resonant frequency is exceeded, a phase shift occurs so that excitation and reaction occur substantially out of phase with one another and the system accordingly operates supercritically. This phase shift which ideally and at most has a value of 180° is made use of by the present invention to achieve the desired reduction in rotational irregularities in that the torque oscillation component that is phase-shifted in this way is superposed with the non-phase-shifted torque oscillation component.
Further, a second phase shifter arrangement can advantageously be provided in the second torque transmission path. This second phase shifter arrangement can also comprise a second oscillation system with a primary side and a secondary side which is rotatable relative to the primary side around the axis of rotation against the action of a spring arrangement.
To ensure that a desired reduction in rotational irregularities is achieved when working with a phase shifter arrangement in the two torque transmission paths, the first oscillation system and the second oscillation system have resonant frequencies that differ from one another. In this way, a frequency range and speed range can be defined in which one of the two torque transmission paths operates in supercritical state, while the other still operates in subcritical state, i.e., without a phase shift.
In so doing, it is preferably provided that the resonant frequency of the first oscillation system is below the resonant frequency of the second oscillation system.
In order to further influence the damping behavior, the first torque transmission path and/or the second torque transmission path is formed with a frictional damping arrangement and/or a fluidic damping arrangement for rotational irregularities transmitted via this torque transmission path.
Of course, the two torque transmission paths can be formed differently, i.e., each of the two torque transmission paths can be formed with or without one and/or the other additional damping aspect.
Particularly when frictional damping and fluidic damping are to be additionally provided in one or both torque transmission paths, a parallel action or serial action thereof can be provided depending on the manner in which they are to influence damping behavior. In this case also, the two torque transmission paths can again also be configured such that they differ from one another.
Further, a diversification of the damping behavior can be achieved in that the frictional damping arrangement and/or the fluidic damping arrangement are/is arranged so as to act in parallel or in series with the spring arrangement.
In an embodiment which is particularly advantageous because of the compact size, the coupling arrangement comprises a planetary transmission arrangement.
In this respect, the construction can be carried out, for example, in such a way that the planetary transmission arrangement comprises a planet gear carrier which is connected to the second torque transmission path and which has a plurality of planet gears rotatably carried thereon.
This means that the torque transmitted into the second torque transmission path is received by the planet gear carrier and then relayed to the output region via the planet gears rotatably carried thereon.
In order that the above-mentioned coupling of the two torque components can also be realized in a simple manner such that there is a destructive superposition, the planetary transmission arrangement comprises a first ring gear arrangement in meshing engagement with the planet gears which is connected to the first torque transmission path and a second ring gear arrangement in meshing engagement with the planet gears which is connected to the output region.
In an alternative embodiment form which makes use of installation space available chiefly in the radially inner region, the planetary transmission arrangement comprises a first sun gear arrangement in meshing engagement with the planet gears which is connected to the first torque transmission path and a second sun gear arrangement in meshing engagement with the planet gears which is connected to the output region.
The behavior by which rotational irregularities can be eliminated in the torque to be transmitted can be influenced further in that the torque components to be introduced into or transmitted by the two torque transmission paths are influenced with respect to magnitude. For example, it can be provided that the first ring gear arrangement or sun gear arrangement in connection with the planet gears and the second ring gear arrangement or sun gear arrangement in connection with the planet gears provide transmission ratios which differ from one another. Through the selection of transmission ratios which are not identical to one another, it is possible to conduct a larger torque component via the first torque transmission path or also via the second torque transmission path.
Since the planetary transmission arrangement acting as coupling arrangement is operative only in a comparatively small angular range permitted by the phase shifter arrangement and the oscillation system thereof, it can further be provided that at least one planet gear and/or the ring gear arrangement and/or the sun gear arrangement are/is constructed in the manner of a segmented gear.
An embodiment which is particularly advantageous for preventing imbalances can be provided in that the planet gears are arranged so as to be substantially circumferentially equidistant from one another. Alternatively, it is possible that the planet gears are arranged at unequal distance from one another circumferentially. By varying the circumferential spacing of the planet gears, it is possible to influence the noise generation thereof and therefore to achieve a quieter running.
Mainly the radially inner installation space is used efficiently when the coupling arrangement is arranged radially inside the first phase shifter arrangement and/or the second phase shifter arrangement and therefore in an at least partially axially overlapping manner.
Alternatively, it can be provided that the coupling arrangement is arranged axially adjacent to the first phase shifter arrangement and/or the second phase shifter arrangement. In this embodiment, it is possible to configure the coupling arrangement so as to be comparatively large in size axially, i.e., with larger effective radii.
A particularly efficient superposition of the oscillation components transmitted via the two torque transmission paths can be achieved when the second torque transmission path has a stiffness of at least 800 Nm/°, preferably at least 1500 Nm/°. This means that the second torque transmission path, or the structural component parts or assemblies providing this second torque transmission path, are comparatively stiff and an elasticity leading to the phase shift is used substantially only in the first torque transmission path.
It has further been shown that the vibration damping characteristic is especially advantageously pronounced when a ratio of a mass moment of inertia of the input region to a mass moment of inertia in the first torque transmission path is in the range of 1 to 10 and/or when a ratio of a mass moment of inertia in the first torque transmission path to a mass moment of inertia in the second torque transmission path is in the range of 2 to 20.
The present invention is further directed to a hybrid drive module and a hydrodynamic coupling arrangement, particularly a hydrodynamic torque converter, with a torsional vibration damping arrangement according to the invention.
Further, the present invention is directed to a drive system for a vehicle comprising a drive unit and a torsional vibration damping arrangement according to the invention, wherein the input region thereof can be coupled to a driveshaft of the drive unit.
In a drive system of this kind, it is advantageously ensured that a resonance of the first oscillation system is below or near the idling speed of the drive unit. With this resonance, i.e., the resonant frequency of the first oscillation system converted into a rotational speed, it is ensured that the phase difference initiated by the occurrence of the phase shift in the region of resonance and the resulting superposition of phase-shifted oscillation components can be utilized practically in the entire speed range.
It can further be provided that a resonance of the second oscillation system is above or near the maximum speed of the drive unit.